This invention relates to an efficient aqueous free radical addition polymerization process for preparing novel water soluble polymer products having a weight average molecular weight less than 30,000. These polymer products are formed from about 3 to about 50 weight percent of at least one monoethylenically unsaturated dicarboxylic acid monomer, and from about 50 to about 97 weight percent of at least one water soluble monoethylenically unsaturated monocarboxylic acid monomer, and from 0 to about 40 weight percent of one or more carboxyl-free monoethylenically unsaturated monomers, based on the total weight of monomers. More specifically, the process of the present invention provides an efficient method of controlling the molecular weight of the polymer product through the use of at least one chain transfer agent and through maintaining the polymerization at an aqueous solution pH of 3 or less. The chain transfer agent has the added benefit, in certain applications, of enhancing the performance of the polymer product.
Polymers of monoethylenically unsaturated dicarboxylic acids, monoethylenically unsaturated monocarboxylic acids, and carboxyl-free monoethylenically unsaturated monomers having weight average molecular weights (Mw) less than 30,000 are useful as scale inhibitors, deflocculants, dispersants, in water circulating systems and as encrustation inhibitors, builders, anti-filming agents, sequestering agents, and dispersants in detergents and cleaning formulations.
A well known problem in preparing these polymers is that it is difficult to control the molecular weight and degree of branching during the preparation of these polymers. The control of molecular weight is especially difficult when preparing polymers containing low levels of monoethylenically unsaturated dicarboxylic acids of from about 3 to about 50 weight percent. Another problem associated with preparing these polymers is that it is difficult to achieve low residual levels of monomer in the polymer product, preferably less than 3.0 weight percent based on the weight of the polymer product.
One solution to controlling the molecular weight of the polymer is disclosed in U.S. Pat. No. 5,100,980 to Hughes et al., hereinafter referred to as xe2x80x9c""980 patent.xe2x80x9d The ""980 patent discloses a process for preparing copolymers containing from about 3 to about 25 weight percent monoethylenically unsaturated dicarboxylic acids and 75 to about 97 weight percent monoethylenically unsaturated monocarboxylic acids having a Mw less than 25,000. The process described in the ""980 patent requires the monomers to be polymerized in the presence of a polymerization initiator, copper salt polymerization moderator, and neutralizer. The presence of the copper salt moderator in the ""980 patent is believed to promote high conversion of the monomers and control the molecular weight of the resulting copolymers.
U.S. Pat. No. 5,244,988 also to Hughes, et al., hereinafter referred to as the xe2x80x9c""988 Patent,xe2x80x9d discloses another process for making low molecular weight copolymers of ethylenically unsaturated dicarboxylic acid monomers. The copolymers in the ""988 patent are produced by cofeeding the monomers and a neutralizer in the presence of a metal salt activator. The copolymers produced have molecular weights ranging from about 1000 to about 100,000 and the cofeeding of the monomers is believed to produce a copolymer of more uniform composition.
However, the processes disclosed in the ""980 and ""988 patents produce a copolymer which is completely or partially neutralized. It may be desirable in some applications for performance or cost reasons to directly produce a polymer product which is not neutralized. Additionally, the ""988 and ""980 patents produce a polymer product which is colored dark yellow to brown due to the processing conditions.
Therefore, it is an aim of this invention to produce polymers formed from 3 to 50 weight percent monoethylenically unsaturated dicarboxylic acids, and 50 to 97 weight percent monoethylenically unsaturated monocarboxylic acids having weight average molecular weights less than 30,000 without using a neutralizer.
It is also an aim of this invention to provide a process for making polymers formed from monoethylenically unsaturated dicarboxylic acids and monoethylenically unsaturated monocarboxylic acids where the resulting polymer product has low color.
It is also an aim of this invention to produce polymers formed from monoethylenically unsaturated dicarboxylic acids and monoethylenically unsaturated monocarboxylic acids having comparable or improved performance over polymers currently in use.
We have discovered an aqueous free radical addition polymerization process comprising:
a) establishing an initial charge of water in a reactor;
b) adding into the reactor to form a reaction mixture
i) at least one water soluble chain transfer agent,
ii) at least one water soluble initiator,
iii) at least one metal promoter,
iv) from about 50 to about 97 weight percent, based on the total weight of the monomer added to the reactor, of at least one water soluble monoethylenically unsaturated monocarboxylic acid monomer,
v) from about 3 to about 50 weight percent, based on the total weight of the monomer added to the reactor, of at least one monoethylenically unsaturated dicarboxylic acid monomer,
vi) from 0 to about 40 weight percent, based on the total weight of the monomer added to the reactor, of one or more water soluble carboxyl-free monoethylenically unsaturated monomers;
c) maintaining the reaction mixture at a temperature of from about 60xc2x0 C. to about 120xc2x0 C. over a reaction time;
d) maintaining the reaction mixture at a pH of 3 or less over the reaction time; and
e) recovering a water soluble polymer product; wherein the chain transfer agent, initiator, and monoethylenically unsaturated monocarboxylic acid monomer are added to the reactor over at least 25 percent of the reaction time.
We have discovered an efficient, cost effective aqueous free radical polymerization process for making a water soluble polymer product formed from a) at least one monoethylenically unsaturated dicarboxylic acid, hereinafter called xe2x80x9cdicarboxylic acid monomerxe2x80x9d, b) at least one monoethylenically unsaturated monocarboxylic acid, hereinafter called xe2x80x9cmonocarboxylic acid monomer,xe2x80x9d and optionally c) one or more carboxyl-free monoethylenically unsaturated monomers, hereinafter called xe2x80x9ccarboxyl-free monomersxe2x80x9d. This process provides a route for making a polymer product containing from about 3 to about 50 weight percent of at least one dicarboxylic acid monomer, from about 50 to about 97 percent of at least one monocarboxylic acid monomer, and from 0 to 40 weight percent of one or more carboxyl-free monomers. The polymer product made by the process of the present invention has a molecular weight less than 30,000. To achieve molecular weights less than 30,000, the process of the present invention uses at least one chain transfer agent and at least one metal promoter in combination with at least one initiator. Additionally, the process of the present invention is conducted at an aqueous solution pH of about 3 or less. Conducting the polymerization at a pH of about 3 or less allows the dicarboxylic acid monomer to react with the other monomers rather than react only with the chain transfer agent.
The process of the present invention has the added advantage of producing a polymer product which has comparable or improved performance properties over polymers currently in use. The resulting polymer product is also low in color which may be desirable to the end user of the polymer product.
In the process of the present invention first an initial charge of water is placed in a reactor. The following ingredients are added to the reactor: i) at least one water soluble chain transfer agent, ii) at least one water soluble initiator, iii) at least one metal promoter, iv) at least one monocarboxylic acid monomer, v) at least one dicarboxylic acid monomer, and optionally vi) one or more carboxyl-free monomers to form a reaction mixture. The reaction mixture is maintained at a reaction temperature of from about 60xc2x0 C. to about 120xc2x0 C. over a reaction time to polymerize the monomers. By xe2x80x9creaction timexe2x80x9d we mean the time over which the ingredients are added to the reactor plus any additional time the reaction mixture is held at the reaction temperature. The reaction mixture is also maintained at an aqueous solution pH of about 3 or less over the reaction time. The chain transfer agent, initiator, and monocarboxylic acid monomer are added to the reactor over at least 25 percent of the reaction time.
The dicarboxylic acid monomer may be added to the reactor over a percentage of the reaction time, or a portion or all of the dicarboxylic acid monomer may be added to the initial charge of water. It is preferred to add the dicarboxylic acid monomer to the reactor by feeding the dicarboxylic acid monomer over a percentage of the reaction time. The dicarboxylic acid monomer is fed over a time of about 10 to 100 percent, preferably from about 10 to about 75 percent, and most preferably from about 15 to about 60 percent of the reaction time.
The dicarboxylic acid monomer may be fed continuously at a linear (constant) or nonlinear rate, or fed intermittently into the reactor. By xe2x80x9cintermittentlyxe2x80x9d we mean the dicarboxylic acid monomer feed to the reactor is turned on and off repeatedly over a percentage of the reaction time. For example, in this intermittent feeding procedure, the dicarboxylic acid monomer may be turned on for a time of from about 10 to about 50 percent of the reaction time and then turned off for a period of about the same time. Preferably, the dicarboxylic acid is fed intermittently.
The metal promoter may be added to the reactor over a percentage of the reaction time, or a portion or all may be added to the initial charge of water. Additionally, the metal promoter may be added to the reactor in one charge at some point in the reaction time. Preferably, the metal promoter is added to the reactor over a percentage of the reaction time. The metal promoter, when added to the reactor over a percentage of the reaction time, may be fed continuously at a linear or nonlinear rate, or intermittently into the reactor. The metal promoter, when added to the reactor over a percentage of the reaction time, may be fed into the reactor from about 1 to about 100 percent of the reaction time.
The chain transfer agent is added to the reactor over at least 25 percent of the reaction time. Optionally, up to 15 percent of the total chain transfer agent added to the reactor may be added to the initial charge of water. Preferably, all the chain transfer agent is fed to the reactor over at least 25 percent of the reaction time. The chain transfer agent is preferably fed to the reactor over at least 30 percent, more preferably from about 40 to about 85 percent of the reaction time. The chain transfer agent may be fed continuously at a linear or nonlinear rate, or fed intermittently into the reactor.
The initiator is added to the reactor over at least 25 percent of the reaction time. Optionally, up to 15 percent of the total initiator added to the reactor may be added to the initial charge of water. Preferably, all the initiator is fed to the reactor over at least 25 percent of the reaction time. The initiator is preferably fed over at least 50 percent of the reaction time. The initiator may be fed continuously at a linear or nonlinear rate, or fed intermittently into the reactor.
The monocarboxylic acid monomer is added to the reactor over at least 25 percent of the reaction time. Optionally, up to 15 percent of the total monocarboxylic acid monomer added to the reactor may be added to the initial charge of water. Preferably, all the monocarboxylic acid monomer is fed to the reactor over at least 25 percent of the reaction time. The monocarboxylic acid monomer is preferably fed over at least 50 percent of the reaction time. The monocarboxylic acid monomer may be fed continuously at a linear or nonlinear rate, or fed intermittently into the reactor.
The carboxyl-free monomer may be added to the reactor over a percentage of the reaction time, or a portion or all of carboxyl-free monomer may be added to the initial charge of water. The preferred way of adding the carboxyl-free monomer depends upon the reactivity of the carboxyl-free monomer. If the reactivity of the carboxyl free monomer is comparable to the monocarboxylic monomer then the carboxyl-free monomer should be added according to the preferred procedures for the monocarboxylic acid. However, if the reactivity of the carboxyl free monomer is comparable to the dicarboxylic monomer then the carboxyl-free monomer should be added according to the preferred procedures for the dicarboxylic acid.
In a preferred embodiment of the process of the present invention, the initiator and monocarboxylic acid monomer are fed into the reactor over the same reaction time. The chain transfer agent is fed for a time less than the initiator and monocarboxylic acid monomer. Preferably the chain transfer agent is fed for a time of about 10 to about 25 percent less than the initiator and monocarboxylic acid monomer. The dicarboxylic acid monomer is also fed for a time less than the initiator and monocarboxylic acid monomer. Preferably the monocarboxylic acid monomer is fed for a time of about 25 to about 75 percent less than the initiator and monocarboxylic acid monomer.
Preferably, the initiator, chain transfer agent, metal promoter, dicarboxylic acid monomer, monocarboxylic acid monomer, and carboxyl-free monomer feeds are all fed in separate streams into the reactor. However, it is possible to combine feeds in accordance to procedures well known to those skilled in the art. For example, where no adverse reactions are expected, the monomers may be combined in one feed stream, or for example, the chain transfer agent and metal promoter may be combined in one feed stream.
In the process of the present invention, the reaction should be maintained at a pH of about 3 or less, more preferably at a pH of about 2 or less, and most preferably at a pH of 1.8 or less. In the most preferred embodiment of the process of the present invention, the monomers containing carboxylic acid moieties are not neutralized with a common base, such as for example sodium hydroxide, prior to being added into the reactor; and no neutralizer is added into the reactor over the reaction time. However, it is possible to add partially neutralized carboxylic acid monomers, or to add a neutralizer into the reactor as long as the pH of the reaction mixture is maintained at a pH of about 3 or less. Possible neutralizers include common bases, for example ammonium hydroxide, or an alkali metal base such as sodium hydroxide, potassium hydroxide, or lithium hydroxide.
The temperature of the reaction mixture over the reaction time should be maintained below the boiling point of the reaction mixture. The reaction mixture temperature should be maintained at a temperature of from about 60 to about 120xc2x0 C., preferably from about 70 to about 100xc2x0 C., most preferably from about 70 to about 80xc2x0 C. over the reaction time. The reaction mixture pressure should be maintained at a pressure of from about atmospheric to about 40 pounds per square inch gauge (psig). Preferably, the reaction mixture pressure is maintained at atmospheric pressure. The polymerization may be conducted in air or any inert atmosphere such as nitrogen or argon.
The dicarboxylic acid monomer which may be used in the process of the present invention includes monoethylenically unsaturated dicarboxylic acids and the anhydrides of the cis dicarboxylic acids containing from 4 to about 10, preferably from about 4 to about 6, carbon atoms per molecule. Examples of suitable dicarboxylic acid monomers include maleic acid, itaconic acid, mesaconic acid, fumaric acid, citraconic add, a-methylene glutaric acid, and the anhydrides of cis dicarboxylic acids, such as maleic anhydride, cis-3,4,5,6-tetrahydrophthalic anhydride, and combinations thereof. Preferably, the dicarboxylic acid monomer is selected from the group consisting of maleic acid, itaconic add, mesaconic acid, fumaric acid, citraconic acid, and the anhydrides of cis dicarboxylic acids, such as maleic anhydride, and combinations thereof; and most preferably is selected from the group consisting of maleic anhydride and maleic acid, and combinations thereof. The weight percent dicarboxylic acid monomer based on the total weight of monomers added to the reactor may be from about 3 to about 50 weight percent, preferably from about 5 to about 35, more preferably from about 5 to about 25, and most preferably from about 5 to about 15 weight percent.
The monocarboxylic acid monomer useful in the process of the present invention includes monoethylenically unsaturated monocarboxylic acids containing from about 3 to about 6 carbon atoms per molecule. Useful monocarboxylic acid monomers include acrylic acid, methacrylic acid, vinylacetic acid, crotonic acid, and combinations thereof. The most preferred monocarboxylic acid monomers are acrylic acid, methacrylic acid, and combinations thereof. The weight percent monocarboxylic acid monomer based on the total weight of monomers may be from about 50 to about 97 weight percent, preferably from about 65 to 95, more preferably from about 75 to about 95, and most preferably from about 85 to 95 weight percent.
The carboxyl-free monomers are water soluble monoethylenically unsaturated carboxyl-free monomers such as for example alkyl esters of acrylic or methacrylic acids such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and isobutyl methacrylate; hydroxyalkyl esters of acrylic or methacrylic acids such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate; acrylamide, methacrylamide, N-tertiary-butylacrylamide, N-methylacrylamide, N,N-dimethylacrylamide; acrylonitrile, methacrylonitrile; allyl alcohol; allylsulfonic acid, methallylsulfonic acid; allyl phosphonic acid; vinylphosphonic acid; dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate; phosphoethyl methacrylate; N-vinylpyrollidone, N-vinylformamide, N-vinylimidazole; vinyl acetate, styrene; vinylsulfonic acid and its salts; and 2-acrylamido-2-methylpropanesulfonic acid and its salts; and combinations thereof. The weight percent carboxyl-free monomer based on the total weight of monomers added to the reactor may be from about 0 to about 40 weight percent, preferably from about 0 to 20, and most preferably from about 0 to 10 weight percent.
The metal promoter enhances the conversion of the dicarboxylic acid monomer to polymer product. Metal promoters useful in the process of the present invention are water soluble transition metal salts such as the salts of cobalt, iron, copper, cerium, nickel, manganese, molybdenum, zirconium, vanadium, zinc, and combinations thereof. Useful water soluble metal salts must be capable of generating the metal ion in an aqueous solution and include the salts of sulfates, nitrates, chlorides, bromides, acetates, phosphates and gluconates; such as for example ferrous sulfate heptahydrate, cuprous acetate, ferrous acetate, manganese acetate, cupric acetate, ferrous and ferric chloride, ferrous and ferric phosphate, cuprous and cupric chloride, cuprous and cupric bromide, cupric nitrate, ferric sulfate, manganese bromide, manganese chloride, and combinations thereof. Preferably, the metal promoter is a water soluble metal salt of iron, copper, and combinations thereof, and most preferably is the water soluble salt of iron.
The concentration in the reaction mixture of the metal promoter should be from about 0.25 to about 250 parts per million (ppm) of the metal ion based on the total weight of the monomers added to the reactor. Preferably the concentration of metal ion is from about 1 to about 25 ppm, and most preferably from about 3 to about 20 ppm.
Suitable water-soluble initiators for the process of the present invention are any conventional free radical water-soluble initiator, water-soluble redox initiator, and combinations thereof. The total initiator added to the reaction mixture should be from about 0.5 to about 25, preferably from about 1 to about 6 weight percent based on the total amount of monomer added.
Suitable free-radical initiators include persulfates, peresters, percarbonates, perphosphates, hydrogen peroxide, certain alkyl hydroperoxides, dialkyl peroxides, ketone peroxides, and azo initiators and combinations thereof. Specific examples of free-radical initiators include for example ammonium persulfate, potassium persulfate, sodium persulfate, sodium perphosphate, ammonium perphosphate, hydrogen peroxide, t-butyl hydroperoxide, di-tertiary butyl peroxide, tertiary-amyl hydroperoxide, methylethyl ketone peroxide, 2,2-azobis(cyanovaleric acid), and combinations thereof.
Suitable water-soluble redox initiators include, but are not limited to, sodium bisulfite, sodium sulfite, persulfates, hypophosphites, isoascorbic acid, sodium formaldehydesulfoxylate and combinations thereof.
A preferred method for making the polymer product of the present invention uses a persulfate initiator such as sodium persulfate or potassium persulfate.
Chain transfer agents useful in the process of the present invention include the alkali metal salts of sulfites such as sodium and potassium sulfite, sodium and potassium bisulfite, and sodium and potassium metabisulfite; halogen containing compounds such as carbon tetrachloride, bromoform, bromotrichloromethane; xcex2-mercaptopropionic acid; C1-C4 aldehydes; mercaptans and thioesters such as hydroxyethyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, octyl mercaptan, tetradecyl mercaptan, hexadecyl mercaptan, butyl thioglycolate, isooctyl thioglycolate, and dodecyl thioglycolate; secondary alcohols such as isopropanol; sulfur containing acids such as thioglycollic acid; and combinations thereof. Preferably the chain transfer agent is an alkali metal salt of sulfite, and is most preferably the alkali metal salt of bisulfite or metabisulfite. The chain transfer agent is used in an amount from about 1 to about 35 weight percent, preferably from about 5 to about 20 weight percent based on the total weight of monomer added to the reaction mixture.
Depending on the chain transfer agent chosen, the chain transfer agent as used in the process of the present invention has the added advantage of being incorporated into the polymer structure and enhancing the performance of the polymer in certain applications.
The process of the present invention may be run as a batch process or a continuous process. By a xe2x80x9ccontinuous processxe2x80x9d, we mean that a portion of the reaction mixture is removed from the reactor as the ingredients are being added into the reactor. In a continuous process, the total rate of ingredients being added into the reactor equals the rate of reaction mixture being removed. The process of the present invention may also be conducted as a semi-continuous process in that part of the process is conducted as a batch process and another part of the process is conducted as a continuous process. Preferably, the process of the present invention is run as a continuous process. The process of the present invention may be carried out in more than one reactor.
The reaction time of the process of the present invention depends on such variables as the amount of metal promoter added to the reaction mixture and the reaction temperature. However, typically in a batch process, the reaction time is from about 1 to about 5 hours. Preferably the reaction time is less than 3 hours, more preferably less than 2 hours. The reaction time may optionally include a hold time in which after all the ingredients are added into the reactor, the reaction mixture is maintained at the reaction temperature of about 60xc2x0 C. to about 120xc2x0 C. The hold time is preferably less than 60 minutes. In a continuous process, the reaction time is the average amount of time the reaction mixture resides in the reactor at the reaction temperature. The reaction time for a continuous process is hereinafter called the xe2x80x9cresidence timexe2x80x9d. The residence time is at least 30 minutes, preferably from about 45 to about 60 minutes.
The weight percent of solids in the reaction mixture, based on the total weight of the reaction mixture at the completion of the reaction time should be from about 30 to about 65 weight percent, and preferably from about 40 to about 60 weight percent.
At the completion of the reaction time, the combined residual level of dicarboxylic acid monomer and monocarboxylic acid monomer in the polymer product should be less than 2.7 weight percent, preferably less than 1 weight percent and most preferably less than 0.5 weight percent, based on the total weight of polymer product.
After the polymerization, the level of residual monomer and chain transfer agent may be optionally reduced by adding one or more initiators, reducing agents, or scavenging monomers which can assist in scavenging unreacted monomer and chain transfer agent. Preferably, any post-polymerization additions of initiators, reducing agents or scavenging monomers are conducted at or below the reaction temperature. Generally, any of the initiators suitable for the polymerization are also suitable for reducing the residual monomer and chain transfer agent content of the polymer mixture.
Typically, the level of initiator, reducing agent, or monomer added to reduce the residual monomer and chain transfer agent content of the polymer product is in the range of from about 0.5 to about 5.0, and preferably from about 1.0 to about 4.0 weight percent based on the total amount of monomer.
After the polymerization, the polymer product may be recovered and used as is, separated by conventional techniques such as spray drying to isolate the polymer solids, or diluted with water to adjust the percent reaction solids to less than 40 weight percent. If desired, excess initiator in the polymer product may be reduced with one or more common reducing agents such as sodium metabisulfite or isoascorbic acid. Additionally, the pH of the polymer product may be adjusted such as for example by adding a common base such as sodium hydroxide.
The weight average molecular weight (Mw) of the polymer product produced by the process of the present invention is from about 500 to about 30,000, preferably from about 1000 to about 20,000, more preferably from about 1000 to about 15,000, and most preferably from about 1,000 to about 10,000 as measured by gel permeation chromatography (GPC) based on a relative standard of 4500 Mw poly(acrylic acid). The polydispersity (the Mw divided by the number average molecular weight, Mn) of the polymer product is less than 2.5 preferably less than 2 and most preferably less than 1.8.
Certain polymer products produced by the process of the present invention are unique in that they show improved performance in comparison to polymers of similar molecular weight and monomer composition made by different processes. These unique polymer products are terminated at one or both ends with the chain transfer agent used in the process of the present invention. The chain transfer agent is selected from the group consisting of alkali metal salts of sulfites, bisulfites, metabisulfite, and combinations thereof. The polymer product is preferably formed from a dicarboxylic acid monomer of maleic acid or maleic anhydride, and a monocarboxylic acid of acrylic acid or methacrylic acid. The polymer product may be partially or completely neutralized after being made.
The polymer product produced by the process of the present invention is useful as an additive in cleaning compositions such as cleaning or detergent formulations used for hard surfaces; household, industrial and institutional laundry; and hand and automatic dishwashing. For example, the polymer product may be used as a builder, encrustation inhibitor, antiredeposition agent, anti-filming agent, sequestering agent, soil removal agent, and dispersant in cleaning and detergent formulations.
The polymer product is also useful for scale inhibition and corrosion control in any water circulating system such as those systems used in cooling water towers, boilers, water desalination plants, sugar recovery plants, oil drilling wells, reverse osmosis equipment, steam power plants, and heat exchange equipment.
The polymer product of the present invention may also be used as a dispersant for inorganic particulates such as pigments, kaolin clay, ceramics, calcium carbonate, zeolites, titanium dioxide; for aqueous emulsions such as latex paints and glazes; and for drilling muds. The polymer product is also useful as a dispersing agent in paper making.
The polymer product is particularly useful as an additive in cleaning compositions such as in cleaning and detergent formulations. Cleaning and detergent formulations containing the polymer product may be in any of the usual physical forms, such as for example powders, beads, flakes, bars, tablets, noodles, liquids, pastes, and slurries. The cleaning and detergent formulations are prepared and utilized in the conventional manner and are usually based on surfactants, and optionally, on either precipitant or sequestrant builders.
Suitable surfactants are, for example, anionic surfactants, such as from C8 to C12 alkylbenzenesulfonates, from C12 to C16 alkanesulfonates, from C12 to C16 alkylsulfates, from C12 to C16 alkylsulfosuccinates and from C12 to C16 sulfated ethoxylated alkanols and nonionic surfactants such as from C6 to C12 alkylphenol ethoxylates, from C12 to C20 alkanol alkoxylates, and block copolymers of ethylene oxide and propylene oxide. Optionally, the end groups of polyalkylene oxides can be blocked, whereby the free OH groups of the polyalkylene oxides can be etherified, esterified, acetalized and/or aminated. Another modification consists of reacting the free OH groups of the polyalkylene oxides with isocyanates. The nonionic surfactants also include C4 to C18 alkyl glucosides as well as the alkoxylated products obtainable therefrom by alkoxylation, particularly those obtainable by reaction of alkyl glucosides with ethylene oxide. The surfactants usable in detergents can also have an amphoteric character and they can be soaps.
In general, the surfactants constitute from 2 to 50, preferably 5 to 45 percent by weight of the cleaning or detergent formulation. Liquid detergent or cleaning formulations usually contain as components liquid or even solid surfactants which are soluble or at least dispersible in the formulation. Surfactants suitable for this purpose are liquid polyalkylene oxides or polyalkoxylated compounds, products that can also be used in powdered detergents.
Examples of sequestrant builders contained in the cleaning and detergent formulations can include phosphates, specifically, pyrophosphates, polyphosphates, and especially sodium tripolyphosphate. Further examples are the zeolites, sodium carbonate, poly(carboxylic acids), nitrilotriacetic acid, citric acid, tartaric acid, the salts of the aforesaid acids and the monomeric, oligomeric or polymeric phosphonates.
The amounts of the individual substances used in the preparation of cleaning and detergent formulations by weight based on the total weight of the formulation are, for example, up to 85 weight percent sodium carbonate, up to 45 weight percent phosphates, up to 40 weight percent zeolites, up to 30 weight percent nitrilotriacetic acid and phosphonates and up to 30 weight percent polycarboxylic acids. In certain liquid detergent markets the use of builders is usually limited to citric acid and its salts or a combination of citrate and fatty acid soap, while in other markets liquid detergent compositions incorporate an intermediate level of soap, about 15 weight percent, or tripolyphosphate, about 20 weight percent, to assist overall cleaning efficacy.
Other common additives to cleaning compositions and especially detergent formulations are bleaching agents, used in an amount of up to 30 weight percent; corrosion inhibitors, such as silicates, used in an amount of up to 25 weight percent; dye transfer inhibiting agents, used in an amount up to 20 weight percent; and graying inhibitors used in an amount of up to 5 weight percent. Suitable bleaching agents are, for example, perborates, percarbonates or chlorine-generating substances, such as chloroisocyanurates. Suitable silicates used as corrosion inhibitors are, for example, sodium silicate, sodium disilicate and sodium metasilicate. Suitable dye transfer inhibiting agents are for example poly(vinyl pyrrolidone). Examples of graying inhibitors are carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose and graft copolymers of vinyl acetate and polyalkylene oxides having a molecular weight of 1,000 to 15,000. Other common optional additives used in cleaning compositions and especially detergent formulations are optical brighteners, enzymes and perfumes.
Powdered detergent formulations can also contain up to 50 weight percent of an inert diluent, such as sodium sulfate, sodium chloride, or sodium borate. The detergent formulations can be anhydrous or they can contain small amounts, for example up to 10 weight percent, of water. Liquid detergents can contain up to 80 weight percent water as an inert diluent.
One or more of the polymer products produced from the process of the present invention can be added to cleaning compositions including cleaning and detergent formulations at levels where they provide the intended benefit. Generally, this level will be from about 0.5 to about 50 weight percent, preferably from about 1 to about 40 weight percent of polymer product, based on the total weight of the formulation. For example, if the polymer product is used as a builder in a detergent or cleaning formulation, the level in the formulation will be from about 5 to about 40 weight percent, based on the total weight of the formulation. In some cases, particularly when used as a soil removal agent and soil redeposition inhibitor, the amount of polymer product actually used is preferably between about 1 and 10 weight percent, based on the cleaning and detergent formulation. Of particular importance is the use of the additives according to the invention in low phosphate detergents and cleaning agents, particularly those containing a precipitant builder such as sodium carbonate. The polymer product of the present invention is particularly useful for the prevention of encrustation in detergent and cleaning formulations containing greater than 50 weight percent sodium carbonate. Low-phosphate formulations contain up to a maximum of 10 weight percent of sodium tripolyphosphate or pyrophosphate.
If desired, the polymer product prepared according to the process of the present invention can be used in detergent formulations together with other acrylic acid homopolymers. The acrylic acid homopolymers are currently being used as soil redeposition inhibitors in detergent formulations. The polymer product can be added to detergent and cleaning formulations in unneutralized, partially neutralized or completely neutralized form.
Other preferred applications for the polymer product produced by the process of this invention include its use in water circulating systems. In water circulating systems, the polymer product may act as a dispersant, and may also act as an anti-nucleating agent where minor amounts of the polymer product can serve as a threshold inhibitor for crystal formation or scaling. Water circulating systems in which the polymer product is useful include those systems used for cooling water towers, boilers, water desalination plants, sugar recovery plants, oil drilling wells, reverse osmosis equipment, steam power plants, and heat exchange equipment. When used to inhibit crystal formation or scaling, the polymers are often combined with corrosion inhibitors such as inorganic or organic phosphates or phosphonates or metallic salts such as zinc compounds and the like.
The polymer product can be added directly to the aqueous system in an amount of 0.1 to 500 ppm by weight. The polymer product may also be added to the system as a concentrated aqueous composition containing one or more inert diluents wherein the polymer product is present in the composition at a level of from 20 percent to 60 percent by weight.